This application is a 371 of WO 97/45449.
This invention relates to dendritic cell receptors. In particular, it relates to human DEC-205, to the production and use thereof, and to ligands which bind to it. Human DEC-205 and its ligands are useful in prophylaxis and therapy.
Dendritic cells perform important immunoregulatory functions by presenting antigens in the form of peptides bound to cell-surface major histocompatibility complex (MHC) molecules to T cells. Identification of the mechanism by which this antigen presentation function is achieved therefore has important implications in manipulating immune response in prophylaxis and therapy, particularly in humans.
Jiang et al, Nature 375: 151-155 (1995) disclose a murine dendritic cell receptor having a molecular weight of 205 kDa (murine DEC-205). However, they do not disclose a receptor on human dendritic cells.
The applicant has now identified a receptor on human dendritic cells. It is broadly to this receptor (likely to be the human homolog of murine DEC-205) that the present invention is directed.
The present invention has a number of aspects. In a first aspect, the invention provides isolated human DEC-205 which has an approximate molecular weight of 198-205 kDa and which includes the following amino acid sequences:
(i) TVDCNDNQPGAICYYSGNETEKEVKPVDSVKCPSPVLNTPWIPF QNCCYNFIITKNRHMATTQDEVQSTCEKLHPKSHILSIRDEKE NNFVLEQLLYFNYMASWVMLGITYRNNSL (amino acids at positions 1208-1323 of SEQ ID NO:1) and
(ii) SQHRLFHLHSQKCLGLDITKSVNELRMFSCDSSAML (amino acids at positions 71-106 of SEQ ID NO:1)
or a functionally equivalent fragment thereof.
In a further aspect, the invention provides isolated human DEC-205 which comprises the amino acid sequence shown in FIG. 11 or a functionally equivalent fragment thereof
In a still further aspect, the invention provides isolated mature human DEC-205, which comprises the amino acids 27 to 1722 shown for human DEC-205 in FIG. 11.
In yet a further aspect, the invention provides an extracellular domain of human DEC-205 or a functionally-equivalent fragment thereof.
In a preferred embodiment, the extracellular domain fragment includes at least a portion of carbohydrate recognition domain (CRD7), spacer, and a portion of carbohydrate recognition domain (CRD8) of human DEC-205 (amino acids 1208 to 1323 of the amino acid sequence of FIG. 11).
In a still further aspect, the invention provides a polynucleotide encoding human DEC-205 or its extracellular domain as defined above. This polynucleotide is preferably DNA, more preferably cDNA, but can also be RNA.
In a specific embodiment, the polynucleotide coding for human DEC-205 includes the following nucleotide sequences (SEQ ID NOS:3and 4, respectively, in order of appearance):
where X is T or G.
In a further embodiment, the polynucleotide comprises part or all of the nucleotide sequence of FIG. 10.
In yet a further aspect, the invention provides a vector including a polynucleotide as defined above.
In still a flrter aspect, the invention provides a method of producing human DEC-205, the extracellular domain thereof or a fimctional fragment comprising the steps of:
(a) culturing a host cell which has been transformed or transfected with a vector as defined above to express the encoded human DEC-205, extracelhular domain or fragment; and
(b) recovering the expressed human DEC-205, extracellular domain or fragment.
As yet an additional aspect, the invention provides a ligand that binds to human DEC-205 or its extracellular domain as defined above.
Preferably, the ligand is an antibody or antibody binding fragment or carbohydrate bearing protein.
The antibody or antibody binding fragment can be used in methods for extracting or isolating activated dendritic cells.
In still a further aspect, the invention provides a construct for use in therapy or prophylaxis. The construct will usually be a ligand-antigen construct or a DEC-205-antigen construct although ligand-toxin and DEC-205-toxin constructs are also contemplated. The ligand-antigen construct preferably consists of an antibody or antibody binding fragment which binds to human DEC-205 and a host-protective antigen. The DEC-205-antigen construct preferably consists of at least the extra-cellular domain of human DEC-205 and a host-protective antigen.
In yet further aspects, the invention contemplates methods of therapy or prophylaxis which employ human DEC-205, ligands or constructs containing them.
In yet a further aspect, the invention provides a molecule (hapten) which may be used to generate antibodies for identifying or puring human dendritic cells, which includes a peptide based upon part or all of the sequence of FIG. 11.